1. Field of the Invention
The invention relates to a fixture for assembling a post-CMP cleaning brush; in particular, to a fixture that assists in the assembly of the post-CMP cleaning brush.
2. Description of the Related Art
As is well known, semiconductor devices are fabricated from semiconductor wafers, which are subjected to numerous processing operations. These operations include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography pattering, etching operations, chemical mechanical polishing (CMP), etc. Although these processes are performed in ultra clean environments, the very nature of many of the process operations is to blame for the generation of surface particles and residue. For instance, when CMP operations are performed, a film of particles and/or metal contaminants are commonly left behind.
Because surface particles can detrimentally impact the performance of an integrated circuit device, wafer cleaning operations have become a standard procedural requirement after certain process steps. Although cleaning operations are rather procedural, the equipment and chemicals implemented to perform the actual cleaning are highly specialized. This specialization is important because each wafer, being at different stages of fabrication, represents a significant investment in terms of raw materials, equipment fabrication time, and associated research and development.
To perform the cleaning operations in an automated manner, fabrication labs employ cleaning systems. The cleaning systems typically include one or more brush boxes in which wafers 1 are scrubbed. As shown in FIG. 1a, each brush box includes a pair of brushes 10, such that each brush 10 scrubs a respective side of a wafer 1. To enhance the cleaning ability of such brush boxes, it is common practice to deliver cleaning fluids through the brush 10 (TTB). Referring to FIG. 1b, TTB fluid delivery is accomplished by implementing brush cores 11 that have a plurality of holes that allow fluids to be fed into the brush core 11 at a particular pressure to be released into an outer brush 12 surface. The outer brush 12 surface is made out of a very porous and soft material so that direct contact with the delicate surface of a wafer 1 does not cause scratches or other damage. Typically, the outer brush 12 surface is made out of polyvinyl alcohol (PVA) foam. Although, other materials such as nylon, mohair or a mandrel wrapped with a polishing pad material can be used. It is noted that the outer brush 12 is provided with a hollow portion 121 for the brush core 11 passing through.
The outer brush 12 must be replaced after cleaning a predetermined number of wafers 1. The conventional method for assembling a new outer brush 12 and the brush core 11 is shown in FIG. 2a, FIG. 2b, FIG. 2c, and FIG. 2d. Firstly, two pads 20, shown in FIG. 2a and made of PVC, are passed through the hollow portion 121 of the outer brush 12 as shown in FIG. 2b. Then, the hollow portion 121 of the outer brush 12 is expanded by pulling the pads 20 while the brush core 11 is passed through the hollow portion 121 of the outer brush 12 as shown in FIG. 2c. Finally, the pads 20 are drawn out of the hollow portion 121 of the outer brush 12 to complete the assembly of the post-CMP cleaning brush 10.
The conventional assembly method has the following disadvantages:
1. Since it is difficult to actually expand the pads 20 into the hollow portion 121 of the outer brush 12, it is difficult to pass the brush core 11 through the hollow portion 121 of the outer brush 12.
2. Since it is difficult to smoothly pass the brush core 11 through the hollow portion 121 of the outer brush 12, the outer brush 12 is easily damaged when the brush core 11 passes through the hollow portion 121 of the outer brush 12.
3. Since the material of the pads 20 is the same as the outer brush 12, it is difficult to draw the pads 20 out of the hollow portion 121 of the outer brush 12. Thus, the pads 20 are easily damaged.